Fastening system for fixing a motor vehicle steering column assembly unit

ABSTRACT

A fastening system for fixing a first assembly unit to a second component for use especially in the motor vehicle industry is presented, which has at least one fastening screw, a corresponding first preassembly thread on the first assembly unit, in which the fastening screw is fixed after the preassembly, and a fastening thread on the first assembly unit or on the second component for fixing the first assembly unit to the second component by means of the fastening screw. The fastening screw has at least two threaded areas for preassembly and for fastening with different thread pitches, wherein the preassembly thread and the fastening thread as well as the threaded areas are provided with different pitches and the second threaded area, which is used for fastening and is facing away from the screw head, has a smaller diameter than the threaded area that is used for the preassembly and is adjacent to the screw head.

FIELD OF THE INVENTION

The present invention pertains to a fastening system for fixing a motorvehicle steering column assembly unit.

BACKGROUND OF THE INVENTION

Such fastening systems are used, e.g., to fix preassembled steeringcolumn assembly units on the body of a motor vehicle within theframework of the final assembly. At the time of the preassembly of asteering column assembly unit, one or more fastening screws are screwedinto a preassembly thread each, which is preferably formed in thehousing of the steering column assembly unit. This offers the advantagethat no individual fastening elements have to be kept ready at the bodyduring the final assembly of the steering column assembly unit. Once thesteering column assembly unit has been brought into its final positionin the course of the final assembly on the body, the fastening screwsare screwed into a second fastening thread. This fastening thread may belocated either directly on the body structure of a motor vehicle or alsoin an extension of the preassembly thread on the steering columnhousing. The steering column assembly unit is clamped in the second caseby a body-side bracket arranged between the preassembly thread and thefastening thread. Both designs of fastening make it necessary for thefastening screw to have its thread leave the preassembly thread beforethe screw enters the fastening thread with its first turns or thepreassembly thread will be broken, i.e., destroyed during the entry ofthe fastening screw into the fastening thread.

Both assembly variants described have one major drawback with respect toa possible removal of the steering column assembly unit.

In the first variant, in which the fastening screw has exited completelyfrom the preassembly thread, the difficulty arises that loosening of thefastening screw inherently means returning of the screw into the firstpreassembly thread. This return is very difficult because the pressingforce can usually be introduced only axially in the longitudinaldirection of the screw and is ruled out nearly completely under thenormal conditions of disassembly. As a result, removal of the steeringcolumn is difficult.

In the second of the above-described variants, the preassembly thread isoften already destroyed completely after the first installation of thesteering column. This means that this thread has to be recut after theremoval of the steering column, because it can no longer be used and theability of the steering column to be mounted is consequently limited.

German publications DE 38 25 177 A1 and DD 145 811 each describe afastening system. Both fastening systems are for fixing a first assemblyunit to a second component, which has a fastening screw. A correspondingfirst preassembly thread is provided on the first assembly unit, inwhich the fastening screw is fixed after the preassembly. A fasteningthread is provided on the second component for fixing the first assemblyunit to the second component by means of the fastening screw, whereinthe fastening screw has two threaded areas for preassembly and forfastening. The second threaded area, which is used for fastening and isfacing away from the screw head, has a smaller diameter than the firstthreaded area, which is used for the preassembly and is adjacent to thescrew head.

Furthermore, U.S. Pat. No. 3,478,639 shows a fastening screw in whichthe preassembly thread and the fastening thread have different pitches.

SUMMARY AND OBJECTS OF THE INVENTION

The primary object of the present invention is therefore to eliminatethe above-described drawbacks of the state of the art and to provide afastening system that guarantees the problem-free assembly and removalof a steering column assembly unit and can be handled without problemsand can be manufactured at low cost.

According to the invention, a fastening system for fixing a motorvehicle steering column assembly unit includes a fastening screw with afirst threaded area and with a second threaded area. A steering columnassembly unit with a steering column housing is provided, in whichhousing a preassembly thread corresponding to the threaded area isprovided. A fastening thread is formed, which is axially aligned withthe preassembly thread and is separated from same in the preassembledstate by a gap. A U-shaped clamp is provided, which is fixed on thesteering column housing. A bracket of the motor vehicle body is disposedat the gap, after the final assembly. This is for connecting thesteering column housing with the motor vehicle body. The fastening screwpasses through an opening in the bracket in the form of a slot or ahole. On the side of the bracket facing away from the preassemblythread, it engages the fastening thread with its second threaded area.With this the clamp is deformed by the movement of the screw. The clampis then in contact with the lateral surfaces of the bracket of the motorvehicle body with its two legs and thus clamps the bracket.

According to an advantageous variant, the fastening thread may beintroduced into a weld nut welded on the clamp.

According to one embodiment of the present invention, it is suggestedthat the fastening screw with at least two threaded areas forpreassembly and for fastening be made with different thread pitches. Thepreassembly and fastening threads on the first assembly unit (and,depending on the design, on the second component) as well as thethreaded areas of the fastening screw are provided with corresponding,different pitches. The second threaded area, which is used for fasteningand is facing away from the screw head of the fastening screw, has asmaller diameter than the first threaded area of the fastening screw.The first threaded area is used for the preassembly and is adjacent tothe screw head.

This special design causes the preassembly thread and the fasteningthread to perform a relative movement in relation to one another in thecase of the simultaneous arrangement of the screw in both threads and acorresponding screw-in movement and thus they can ultimately bring aboutclamping forces that permit the fixation of the steering column assemblyunit on an intermediate plate fixed on the body. Both the turns of thefastening thread and of the preassembly thread remain completely intactduring the fastening operation, so that a problem free removal of theassembled components is possible at any time in a simple manner and at alow cost.

Depending on the application and the space conditions of theconstruction to be used, the fastening system may be designed such thatthe thread pitch of the first threaded area is greater or smaller thanthe thread pitch oft second threaded area of the fastening screw. Thisfreedom, as to modifying the design, expands the possible applicationsof the fastening system to other technical areas. The present inventionis not limited to the above-described special field of application of asteering column fastening.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich preferred embodiments of the invention are illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a sectional representation of an embodiment of the fasteningsystem according to the present invention in the preassembled state and

FIG. 2 is a sectional representation of the fastening system accordingto FIG. 1 after the final assembly in the fixed state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in particular, the fastening system shown inFIGS. 1 and 2 has a fastening screw 3 with a first threaded area 1 andwith a second threaded area 2. The fastening system is used to fix amotor vehicle steering column assembly unit, but only details of thissteering column assembly unit are shown in the representations selectedhere. The steering column assembly unit has a steering column housing 5,in which a preassembly thread 6 is arranged. A fastening thread 8 isarranged axially aligned with the preassembly thread 6 and separatedfrom same by a gap 7. The fastening thread 8 is located in a weld nut 9,which is welded to a U-shaped clamp 10, which is in turn fastened to theabove-mentioned steering column housing 5.

The preassembled state of the steering column assembly unit provides forthe fastening screw 3 with its threaded area 1 being screwed into thepreassembly thread 6 of the steering column housing 5. Within theframework of the final assembly, during which the steering columnassembly unit is fixed in its final position to the motor vehicle body,a bracket 11 of the body is provided in the gap 7 of the steering columnhousing. The fastening screw 3 now passes through an opening 12 in thebracket 11 in the form of a slot or a hole. On the side of the bracket11 facing away from the preassembly thread 6, the fastening screw 3engages, with its second threaded area 2, the fastening thread 8. Thethreaded area 1 has a diameter d₁, with a pitch s₁. Compared with thedimensions of the threaded area 1, the diameter d₂ of the fasteningthread area 2 is such that it can pass through the preassembly thread 6without touching the wall surfaces. The pitch S₂ of the threaded area 2is selected to be greater than the pitch s₁ of the threaded area 1. Theeffect of this arrangement is that the screwing in of the fasteningscrew 3 in the direction of the arrow P, with the threaded area 1engaging the preassembly thread 6 and with the threaded area 2 engagingthe fastening thread 8, causes the weld nut 9 to be displaced on thefastening screw 3 such that the width of the gap 7 will decrease.

FIG. 2 shows the sectional representation of the end position of thefastening screw 3. The clamp 10 has been deformed due to the movement ofthe weld nut 9 on the fastening screw 3 to the extent that the two legs15 and 16 of the clamp 10 have come into contact with the lateralsurfaces of the bracket 11 of the body and they clamp the bracketbetween them. The steering column housing 5 is thus rigidly connected tothe body.

The loosening of the connection between the steering column housing andthe body is performed analogously by turning the fastening screw 3opposite the direction of the arrow P, while the weld nut 9 and,together with it, the leg 15 will move in the direction of the arrow Con the fastening screw 3. As a result, the clamped connection betweenthe two legs 15 and 16 of the clamp 10 and the body bracket 11 iseliminated and the steering column housing 5 can be removed.

It is, of course, conceivable to select the pitch s₂ of the threadedarea 2 to be smaller than the pitch s₁ of the threaded area 1, but theclamping between the bracket 11 and the steering column housing 5 or theclamp 10 takes place analogously to the above-described manner.

While specific embodiments of the invention have been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A motor vehicle steering column assembly unit fastening system, comprising: a fastening screw with a first threaded area and with a second threaded area; a steering column assembly unit with a steering column housing, said steering column housing having a preassembly thread corresponding to said first threaded area; a part having a fastening thread, which is axially aligned with said preassembly thread and is separated from said preassembly thread by a gap in a preassembled state; a U-shaped clamp fixed on said steering column housing, said U-shaped clamp having two legs; a motor vehicle body bracket having lateral surfaces and having an opening, said motor vehicle body bracket being disposed in said gap after a final assembly connecting said steering column housing to the motor vehicle body, said fastening screw passing through said opening in said motor vehicle body bracket, said second threaded area engaging said fastening thread on a side of said bracket facing away from said preassembly thread such that said clamp is deformed by a screwing movement of said fastening screw and said two legs are in contact with said lateral surfaces of said bracket of said motor vehicle body and thus clamp said bracket.
 2. The fastening system in accordance with claim 1, wherein said fastening thread is provided in a weld nut welded to said clamp.
 3. The fastening system in accordance with claim 2, wherein a thread pitch of said first threaded area is greater than a thread pitch of said second threaded area.
 4. The fastening system in accordance with claim 2, wherein the thread pitch of said first threaded area is smaller than the thread pitch of said second threaded area.
 5. The fastening system in accordance with claim 1, wherein said fastening screw has a screw head, said first threaded area has a first thread pitch and said second threaded area has a second thread pitch, said first thread pitch being different from said second thread pitch, said preassembly thread having said first thread pitch and said fastening thread having said second thread pitch, said second threaded area being for fastening and spaced away from said screw head and having a smaller diameter than said first threaded area, first threaded area being used for the preassembly and being adjacent to said screw head.
 6. The fastening system in accordance with claim 5, wherein a thread pitch of said first threaded area is greater than a thread pitch of said second threaded area.
 7. The fastening system in accordance with claim 5, wherein the thread pitch of said first threaded area is smaller than the thread pitch of said second threaded area.
 8. The fastening system in accordance with claim 1, wherein a thread pitch of said first threaded area is greater than a thread pitch of said second threaded area.
 9. The fastening system in accordance with claim 1, wherein the thread pitch of said first threaded area is smaller than the thread pitch of said second threaded area.
 10. A motor vehicle steering column assembly unit fastening system, comprising: a fastening screw with a preassembly threaded area and with a fastening threaded area; a steering column assembly unit with a steering column housing, said steering column housing having a preassembly thread corresponding to said preassembly threaded area; a structural part defining a fastening thread, which is axially aligned with said preassembly thread and is separated from said preassembly thread by a gap in a preassembled state; a U-shaped clamp fixed on said steering column housing, said U-shaped clamp having two legs; a motor vehicle body bracket having an opening, said motor vehicle body bracket being disposed in said gap after a final assembly for connecting said steering column housing to the motor vehicle body, said fastening screw passing through said opening in said motor vehicle body bracket and engaging said fastening thread, with said fastening threaded area, on a side of said bracket facing away from said preassembly thread such that said two legs of said clamp, deformed by a screwing movement, are in contact with lateral surfaces of said bracket of said motor vehicle body and thus clamp said bracket.
 11. The fastening system in accordance with claim 10, wherein said structural part is a weld nut welded to said clamp.
 12. The fastening system in accordance with claim in 10, wherein said fastening screw has a screw head, said preassembly threaded area has a first thread pitch and said fastening threaded area has a second thread pitch, said first thread pitch being different from said second thread pitch, said preassembly thread having said first thread pitch and said fastening thread having said second thread pitch. 